Design and Modeling of Proton-Conducting Bilayer Electrolytes Using a Nernst-Planck-Poisson Formulation

Abstract

In this study, the efficiency of proton-conducting ceramic fuel cells was improved by designing bilayer electrolytes with high ion conductivity and low hole conduction. The designs were carried out by finding the thicknesses of anode and cathode-side electrolytes that optimizes efficiency using integral equations based on Wagner theory. Results obtained for bilayer electrolytes were compared with those of single-layer electrolytes. Best performances were found when thin layers of lanthanum tungstate (La28-x W4+x O54+3x/2v2-3x/2) with an La/W ratio of 6.7 (LWO67) were used as cathode-side electrolytes attached to commonly used perovskite materials like BaCe0.9Y0.1O3- δ (BCY10), BaZr0.8Y0.2O3- δ (BZY20), and BaZr0.1Ce0.7Y0.1Yb0.1O3- δ (BZCYYb1711). In addition, the transport properties of a single-layer LWO67 electrolyte were further analyzed by using the Nernst-Planck-Poisson (NPP) model for which parameters were fitted. Finally, a bilayer NPP formulation was explored to obtained the charged defect fluxes and other useful information to enhance the efficiency of a bilayer BZY20|BZCYYb1711 electrolyte.

Design and Fabrication of Protonic Ceramic Fuel Cells Based on BaZr0.8Y0.2O3−δ |BaZr0.1Ce0.7Y0.1Yb0.1O3−δ Bilayer Electrolyte

“…35,39 Theoretical investigations showed that a thin layer of lanthanum tungstate (LWO; La 27.8 W 4.2 O 54+δ v 2−δ ) can effectively block hole conduction, leading to reduced leakage currents. 40,41 z E-mail: otomo@tse.ens.titech.ac.jp Later, these results were experimentally proven in a different study, in which a bilayer electrolyte containing BZY and LWO exhibited an open circuit voltage (OCV) higher than that of an equivalent BZY single-layer electrolyte. 42 Thus, LWO is capable of reducing the leakage current.…”

“…As per theoretical calculations, a BZY| BZCYYb bilayer would offer no significant improvements to PCFCs. 40,41 However, activation overpotentials were not considered and experimental tests remain to be performed.…”

Bilayer Cell Model and System Design of Highly Efficient Protonic Ceramic Fuel Cells

“…In previous studies, lanthanum tungstate, La28-xW4+xO54+3x/2v2-3x/2 with a La/W ratio of 6.7 (LWO) was successfully used as a hole-blocking layer in a bilayer electrolyte to suppress leakage current (1)(2)(3). Additionally, it was shown that a bilayer electrolyte, made of BaZr0.8Yb0.2O3−δ (BZYb) and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb), can reduce the interfacial resistance between the cathode and the electrolyte and can also prevent nickel diffusion from the anode due to high-temperature cell fabrication processing (4).…”